Social isolation and low social support are associated with increased risk of coronary heart disease and death, presumably through the mechanism of cardiovascular and neuroendocrine reactivity to potential stressors. There is mounting evidence of an association between social support and psychophysiological responses, but the experimental studies have not examined support in the context of actual social network relationships, nor have they examined the likely moderating effects of trait hostility and relationship quality. Further, the role of stress reducing neuroendocrine bases of affiliation and attachment have not been examined in this context. The studies proposed will address these issues in married couples. Couples will complete one of three dyadic interaction tasks (supportive, neutral, or conflictual), followed by individual participation in a stressful speaking task. Concurrent effects of supportive and conflictual social interaction on blood pressure, catecholamine, cortisol and oxytocin responses will be examined, as will "carry over" effects of social interaction on changes in these same variables during the subsequent stressful task. We predict that supportive interactions between spouses will be associated with decreased concurrent and subsequent cardiovascular, catecholamine, and cortisol responses, and that conflcitual interactions will heighten these responses. Further, we will examine changes in oxytocin as a possible mediator of these effects. We also expect that individual differences in trait hostility and prior relationship quality will moderate the concurrent and carryover effects of social interaction on these physiological responses. Study one will test the moderation of these effects across the age range of 18 to 50 years. Study two will compare these effects in Caucasians and African Americans. Explication of the psychobiology of social support and related psychosocial risk factors in personal relationships could guide the refinement of risk reducing, preventive interventions. [unreadable] [unreadable]